1. Field of the Invention
This invention relates to a high activity titanium trichloride catalytic component which is advantageously usable in the manufacture of highly stereospecific .alpha.-olefin polymers and also to a method of homo- or co-polymerization of .alpha.-olefin in which a highly crystalline polymer can be advantageously manufactured in the presence of said catalytic component and an organo-aluminum compound. More specifically stated, the invention relates to an .alpha.-olefin polymerizing titanium trichloride catalytic component which is prepared by precipitating said catalytic component from a solution prepared by dissolving titanium tetrachloride, an organic ether compound and an organo-aluminum compound having the generic formula AIR.sub.n X.sub.3-n (wherein R is an alkyl group having a carbon number of 1 to 10 (i.e., 1 to 10 carbon atoms), X is a halogen or hydrogen atom and n is a real number of 0&lt;n.ltoreq.3), in a solvent comprising an aliphatic hydrocarbon and/or alicyclic hydrocarbon. The organo-aluminum compound is added at a solvent temperature of 55.degree. C. or lower in the concomitant presence of an aromatic hydrocarbon halide and, following this, the solvent temperature is adjusted to between 45.degree. and 150.degree. C. over a period of time 10 minutes to 24 hours to obtain the titanium trichloride catalytic component having an uniformed particle diameter between 10 and 1000.mu.. This invention also relates to a method for carrying out homo- or co-polymerization of .alpha.-olefins in the presence of a catalyst system comprising the titanium trichloride catalytic component and an organo-aluminum compound.
It is the most important feature of the invention that the average particle diameter of the titanium trichloride catalytic component which is precipitated from solution in accordance with the invention is adjustable within the wide range from 10 to 1000.mu. as desired and that the catalytic component thus obtained is highly active when it is used for the polymerization of .alpha.-olefins. In addition, polymers of extremely uniform particle diameter can be obtained by carrying out homo- or co-polymerization of .alpha.-olefins with a catalyst which is prepared using this catalytic component in combination with an organo-aluminum compound. In case of .alpha.-olefin polymers prepared in accordance with the method of this invention, the deashing process and the washing process which are normally considered indispensable in the manufacture of an .alpha.-olefin polymer can be either omitted or simplified. Further, in accordance with this invention, a pelletizing process can also be omitted.
2. Description of the Prior Art
Nowadays, a catalytic component usable for .alpha.-olefin polymerization is required (a) to have a polymerizing activity sufficiently high to permit omission of the deashing and washing processes for removal of catalyst residue and non-stereospecific polymer from the polymer produced, (b) to have a high productivity for a stereospecific polymer and (c) to ensure that the catalytic component and the polymer produced therewith have a suitable particle diameter and a uniform particle size. The reason for such requirements lies in the fact that the catalytic components and the polymer products of conventional methods are obtained in a powdery state having uneven particle sizes which makes separating, drying and transporting them difficult. This has caused trouble in the manufacturing operations and has lowered industrial productivity.
It is also desired that a catalyst or catalytic component permits omission of a pelletizing process in the manufacture of an .alpha.-olefin. In an .alpha.-olefin polymer manufacturing plant using a titanium trichloride catalytic component which is obtained by a conventional method, the powdery polymer obtained is dried and pelletized for melting kneading, extruding and molding before it is shipped as polymer product for use in molding processes. At such an .alpha.-olefin polymer manufacturing plant, the pelletizing process is expensive and consumes a great amount of energy. Preparation of a catalytic component that permits the manufacture of a polymer which is highly homogeneous in particle diameter distribution is free of minute polymer particles would enhance the operational efficiency of the polymer manufacturing plant and eliminate troublesome process of pelletizing the polymer product. This would reduce the cost of facilities and energy consumption, thereby contributing greatly to the economical operation of the polymer manufacturing processes. Therefore, development of such an ideal catalytic component has been strongly desired.
Heretofore, Ziegler-Natta catalysts have been generally employed in the polymerization of .alpha.-olefins. A typical example of such catalysts is a catalytic system consisting of a combination of a .delta.-type titanium trichloride-aluminum chloride eutectic mixture (hereinafter called the .delta.-type eutectic mixture) and an organo-aluminum compound. The .delta.-type eutectic mixture is obtained by pulverizing and activating, in accordance with a known method using a ball mill, a vibration mill or the like, a .gamma.-type titanium trichloride-aluminum chloride eutectic mixture (hereinafter called the .gamma.-type eutectic mixture) which is obtained by reducing titanium tetrachloride with aluminum powder in the presence of aluminum chloride. However, with the .delta.-type eutectic mixture employed as a catalyst component for .alpha.-olefin polymerization, both polymerization activity and the productivity of stereospecific polymer are low and unsatisfactory. There have been proposed many methods for reformation the .delta.-type eutectic mixture, including for example: (1) A method of co-pulverizing the .delta.-type eutectic mixture or the .gamma.-type eutectic mixture and a reforming agent such as an electron donor compound or allowing them to react upon each other; (2) a method of washing the .gamma.-type or .delta.-type eutectic mixture with an inert hydrocarbon solvent; and (3) a method of heating the .gamma.-type or .delta.-type eutectic mixture. The reformation or denaturation by these methods improves the polymerization activity of the catalytic component and the productivity of a stereospecific polymer to a certain degree. Such methods, however, are utterly incapable of controlling the particle diameter of the catalytic component and also are far from meeting the requirement of obviating the necessity of the deashing and washing processes.
Recently, there has been developed some catalytic components which have a high polymerization activity and ensure a high degree of productivity of a stereospecific polymer. An example of methods for obtaining such catalytic components is a method disclosed by Japanese laid-open patent application No. 47-34478. In this method, (1) a .beta.-type titanium trichloride is prepared by reducing titanium tetrachloride with an organo-aluminum compound at a low temperature; (2) a portion of the aluminum compound is removed from the resulting .beta.-type titanium trichloride eutectic mixture by treating the .beta.-type titanium trichloride eutectic mixture with a complex-making agent; and then (3) heat-treating it in titanium tetrachloride to obtain a .delta.-type eutectic mixture having a dark purple color. The catalytic component is excellent-having polymerization activity several times greater than that of a catalytic component of the .delta.-type eutectic mixture which is prepared by the above stated pulverization process. This method for the manufacture of a catalytic component, has the following drawbacks: (1) a long period of time is required for its manufacture; (2) a large quantity of a washing liquid is required for washing the catalytic component; (3) a large quantity of waste liquid containing titanium ions and aluminum ions results; and (4) it necessitates the use of a large quantity of a neutralizing reagent and thus requires a great amount of energy to prevent environmental pollution and to recover the solvent used. This results in a very high manufacturing cost.
To eliminate the above stated drawbacks, there have been proposed improved methods for manufacturing a catalytic component. These improved methods include: (1) A method which has been disclosed in Japanese laid-open patent applications Nos. 51-16298 and 51-76196 in which a liquid matter obtained by treating titanium tetrachloride in the presence of an organic ether compound with an organo-aluminum compound expressed by a generic formula of AlR.sub.n X.sub.3-n (wherein R represents an alkyl group having 1 to 10 carbon atoms; X a halogen atom; and n a real number of 0&lt;n.ltoreq.3) is brought into contact with a liberating agent such as Lewis acid at a temperature not exceeding 150.degree. C. (2) An improvement over the above stated method (1) not using the liberating agent used in the method (1) (this improved method has been disclosed in Japanese laid-open patent application No. 52-47594). (3) A method which has been disclosed in Japanese laid-open patent application No. 51-94496 and in which a titanium trichloride catalytic component is crystallized by using seed crystals in carrying out the above state method (1). (4) A method which has been disclosed in Japanese laid-open patent application No. 51-90998 and in which a titanium trichloride catalytic component is separated out by varying the operating temperature in carrying out the above stated method (1). Each of these catalytic component manufacturing methods does not require the use of a solvent in large quantity and, accordingly, produces only a small quantity of waste liquor. However, each of them has a drawback in that the average particle diameter of the titanium trichloride catalytic component obtained by the method is at the most about 30.mu. and normally measures only several .mu.. Thus, the catalytic component is obtained in an extremely small particle size and at low bulk density which causes the catalytic component to be difficult to handle. Further, when the catalytic component is used for .alpha.-olefin polymerization, the particle diameter of the polymer product is small, its bulk density is low, and yield of stereospecific polymer is low.
As described in the foregoing, properties of the catalytic components for .alpha.-olefin polymerization manufactured by conventional methods and those of the .alpha.-olefin polymers polymerized in the presence of such catalysts are not satisfactory. Therefore, further improvement over these conventional catalytic components is desired.
The inventors of the present invention strenuously conducted studies for a method of manufacturing a titanium trichloride catalytic component which has a high degree of polymerizing activity as well as a high productivity for a stereospecific polymer and which, at the same time, permits free control of the particle diameter of such catalytic component, and also permits control of the particle diameter of the .alpha.-olefin polymer product. As a result of these studies, the applicants have completed the present invention.